Sunday 1 February 2015

Occam's Si5351

This post describes the application of the Si5351 in a simple QRP CW transceiver from the "Occam" series of rigs...

The recently described Si5351 system under development is intended to be a development of the Kanga / m0xpd DDS Shield and to offer backward compatibility with that system. One of the important features of the DDS shield was the "RF Bus", by which RF signals were passed to other shields in the beacons and rigs arising from the "Occam's Microcontroller" project.

To achieve backward compatibility, the new Si5351 system has an enhanced RF Bus, using a double row connector, one row of which is in the same position as the single row on the original DDS Shield...

This allows e.g. the header pins of the Kanga / m0xpd Sudden Tx Shield to plug into the new Si5351 board and to run as a beacon transmitter system. As part of the development of the new Si5351 system, it was time yesterday to confirm such cooperation...

Rather than just validate operation of the transmitter system with the new Si5351 board, I decided also to resurrect the prototype Sudden Rx shield - first seen in the "Occam's Dagger" rig - and try to run a complete transceiver with the new Si5351 shield...

The rig includes a stack of four shields; the controlling Arduino UNO, the new Si5351, The Kanga Sudden Tx and the (prototype) Sudden Rx. The new Si5351 board is of lower height than the old DDS shield, making the entire system rather less cumbersome, as seen in the photo above and in the annotated photo below...

The Occam's Dagger rig also featured my AF, analog CW filter, published in SPRAT 146, which makes the entire system rather more pleasant to use. The new "Occam's Si5351" embodiment of the rig is pleased to preserve that useful feature!

The switch to the new Si5351 RF generator was an easy change - the code modification was very easy to make, so there is now an updated version of the code, supporting the Si5351 and with all the original Occam's Dagger features (automated CQ calls, multi-band operation, etc) available here .

The system worked first time - and my brief "validating QSO" was with Steve, 2e0fck, down in Oxford. Steve was using an old ww2 rig - a nice example of the old rubbing shoulders with the new.

The Si5351 board is getting closer now - watch this space. What's more, there is a growing feeling that it might be interesting to release the Sudden Rx Shield as a commercial item - another reason to watch!

...-.- de m0xpd

A couple of hours later, I turned on the rig again and the very next station I worked was Gerald, g3mck - who was the first station ever worked on the original Occam's Dagger. Small world, isn't it.

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